It has been known since 1932 that human subjects tend to secrete high concentrations of acid into the stomach lumen during the night, and that this phenomenon is often related to peptic ulcer formation. (See, in general, Henning, N. and Norpoth, L., Deutsches Arch. Klin. Med. 178, 558, 1932 and Dragstedt, L. R., Ann. N.Y. Acad. Sci. 99: 190, 1962).
It also has been clear that there is a diurnal rhythm of gastric acid secretion, and that knowledge of this rhythm would aid the diagnosis and treatment of peptic ulcer disease. It has been stressed that it is the acid concentration at night, rather than the total volume of acid secreted in the gastroduodenal lumen, that is the inductive feature of peptic ulcer and erosion formation. On the basis of this knowledge, it has been recommended that anti-ulcer drugs be administered to diminish acid release during the night. (See Fitzpatrick, W. J. F., Blackwood, W. S., and Northfield, T. D., Gut, 23, 239, 1982).
All of the work described in the above cited references was carried out by inserting a tube into the gastroduodenal lumen, removing samples of secretion, and measuring the pH of the sample externally using a pH meter. This method has several disadvantages:
(a) Only a few samples could be measured over a limited time period, thus increasing the likelihood of error in results extrapolated from little data;
(b) The gastroduodenal lumen had to be free of solid matter and food, a condition which invalidated the pH measurement and excluded observations after meals; and
(c) The patient had to be investigated in the clinical setting, where, divorced from his or her daily routine, the patient may evidence higher than normal acid concentrations due to the stress involved.
A recent approach to improving such pH measurements involves the use of an in-dwelling pH-electrode placed in the gut for a period of 24 hours or longer. The electrode is connected to a battery-powered, portable digital storage device capable of storing 17-18K pH values over a 24 hour period. See Fimmel, C. J., Etienne, A., Cilluffo, T., von Ritter, C., Gasser, T., Rey, J. P., Caradonna-Moscatelli, P., Sabbatini, F., Pace, F., Buehler, H. W., Bauerfeind, P., Blum, A. L., Gastroenterology 88, 1842, 1985. This apparatus has the advantages that it enables the patient to go about his normal daily routine, eat a normal diet, indulge in such activities as coffee-drinking and smoking, and even take medications. If times are separately recorded, all of this data can be collected for accurate analysis.
A number of other devices use a modified approach, but the general method is the same as that of Fimmel, et al. All of these devices, however, have one or more of the following significant disadvantages:
(a) Some have a separate external reference electrode which is attached to the skin, which is a source of error. Use of a combined pH electrode is more accurate and has been fully validated.
(b) The portable apparatus only stores data. In order for the physician to see the data (see Fimmel, et al.) the storage element must be connected to a separate computer and the data must be off-loaded and stored on a computer disc or tape, a process which takes about 30 to 60 minutes. The computer then has to be programmed to process the data, e.g. to calculate mean or median values per selected unit time, to calculate the per cent distribution or absolute number of values vs. various pH levels, and to plot out mean or median pH values vs. time over a 24 hour period. This results in a large expense for the accessory equipment and presupposes the ability of the physician to program and operate the external computer to obtain a readable printout with diagnostic or therapeutic significance. A further disadvantage is that software for external computer data processing is not yet commercially available for all machines. All of these disadvantages severely limit the use of such a diagnostic or therapeutic procedure in clinical practice.
It is an important object of this invention to provide an inexpensive and useful apparatus for the measurement of pH within the gastrointestinal tract.
It is a further object of this invention to provide a portable apparatus which houses all the necessary components to fully therapeutically evaluate intragastric function as it relates to pH.
It is a further object of this invention to provide a means for measuring pH within the gastrointestinal tract over a long period of time, storing, calculating, evaluating, indicating (at any selected time, and printing out the pH data.
It is a further object of this invention to provide a portable apparatus for evaluating the diurnal rhythm of intragastric pH which allows measurement of the effects of eating, drinking coffee or alcohol, smoking, and ingesting drugs on intragastric pH.
It is a further object of this invention to provide a portable apparatus for evaluating intragastric pH which allows a physician to prescribe the best possible drug and dosage regimen for a patient with ulcer disease or to determine if certain therapy is having the desired effect on intragastric pH.
In accordance with the above objectives, this invention comprises a portable apparatus having a pH electrode for measuring intraluminal acid concentration, means for measuring the time at which such pH measurement is taken, and a means for receiving and storing the measured value of the concentration of acid and the time at which such measurement was taken.
The apparatus of this invention further includes means for displaying any stored measurement of acid and the time at which such measurement was taken including a present measurement and time, and means for receiving and storing pre-selected pH values.
The apparatus of this invention further includes means to compare a measured pH value with a pre-selected threshold pH value, and means to give an output warning signal when the measured pH value is greater than or less than the pre-selected threshold value, and means, such as a control unit microprocessor, to control the distribution of signals to the various functional subunits.
Other aspects of the invention will become apparent from the description which follows, when taken in conjunction with the accompanying figures.